Snowboard binding assembly

ABSTRACT

An apparatus for gliding on snow with improved stability and better edge-setting in turns includes a single board having a raised tip at the front and a heel at the rear, and a safety binding assembly for securely joining boots to the board. The safety binding assembly includes first and second bindings positioned on the board to prevent movement and rotation in translation, and to form an angle between 0 and 20 degrees relative to the longitudinal axis of the board. The bindings are longitudinally displaced so that the longitudinal distance between them is at most equal to 100 millimeters. The sides of the board include center portions which are concave in shape between the tip and heel of the board, and rectilinear portions located where the center portions of the sides intersect with the tip and heel of the board.

BACKGROUND OF THE INVENTION

The present invention relates to a piece of sporting equipment forgliding on snow of the type constituted by a single board with a raisedtip, on which two bindings for solidly joining boots with the board canbe mounted.

Two types of gliding equipment for snow using a single board are known.This would include monoskis, as disclosed for example in French Patent2,604,631 or U.S. Pat. No. 3,947,049, in which the two bindings areparallel and disposed on the same transverse line, or snowboards, asdisclosed for example in French Patent 2,600,548, in which a frontbinding is oriented longitudinally and a rear binding is orientedtransversely, so that the user is placed in a semi-lateral position.

Two hybrid gliding devices have also been proposed. For example, GermanPatent 25 57 275 discloses a monoski constituted by a board on which thebindings are longitudinally offset, one behind the other. In order tocompensate for the described device's lack of maneuverability, the boardhas a convex profile and the skier uses a small guide rope attached tothe front of the board, which allows the skier to provide the impetusfor entering a turn. German Patent 39 03 401 discloses another suchgliding device.

SUMMARY OF THE INVENTION

It is the primary object of the present invention to provide a piece ofgliding equipment which is constituted by a single board, and which iscapable of causing sensations that are different from those producedwith prior equipment.

It is also an object of the present invention to provide a piece ofgliding equipment which is constituted by a single board, and which iscapable of being used on powdery snow as well as on packed trails.

It is also an object of the present invention to provide a snowboardwhich provides the user with a better view of the slope, particularlyduring the end phase of a turn, when the user is supported on his toesand has their back to the slope.

These and other objects which will be apparent are achieved inaccordance with the present invention by providing an apparatus forgliding on snow which is comprised of a single board, a first bindingwhich is positioned on the board in a way that is not movable inrotation or in translation, and so that the longitudinal axis of thefirst binding forms an angle between 0 degrees and 20 degrees, andpreferably between 4 and 16 degrees, with the median longitudinal axisof the board, and a second binding which is positioned on the board in away that is not movable in rotation or in translation, and so that thelongitudinal axis of the second binding forms an angle between 0 degreesand 20 degrees, and preferably between 4 and 16 degrees, with the medianlongitudinal axis of the board, wherein the bindings are longitudinallydisplaced so that the longitudinal distance between the front end of therear boot and the rear end of the front boot is at most equal to 100millimeters. As a result, the user's head and shoulders are naturallypositioned over the tip of the board, and the user's feet are positionedsubstantially one behind the other.

Preferably, the median axes of the two bindings are parallel, and thebindings are positioned symmetrically relative to an oblique axis whichforms an angle between 4 and 16 degrees with the longitudinal axis ofthe board.

In a preferred embodiment, the width of the board at the center issubstantially equal to 1.5 times the width of one boot. The width of theboard at its center is advantageously between 110 millimeters and 150millimeters, and is preferably on the order of 140 millimeters.

Such a gliding device offers improved ease of use and greatermaneuverability.

In a first variant, the middle point of each of the bindings ispositioned on the median longitudinal axis of the board. Further, thebindings are in parallel and positioned one behind the other so that thetoe of the front binding reaches one of the lateral sides of the board,and the heel of the rear binding reaches the opposite lateral side ofthe board. The median axes of the two bindings are in parallel and forman angle of approximately 7° with the median longitudinal axis of theboard.

In a second variant, the toe of the front binding and the heel of therear binding are positioned on the median longitudinal axis of theboard, and the toe of the rear binding and the heel of the front bindingare positioned on opposite lateral sides of the board. The toes andheels of the user's two feet form a supportive polygon that isdiamond-shaped relative to the median longitudinal axis of the board,which ensures satisfactory balance on the gliding apparatus.

Preferably, the board includes a rounded tip, a central portion havinglateral edges defined (on either side) by the arcs of a circle or anellipse, and a heel with a straight lateral segment on each side of theboard, providing the board with a "wasp waist" or central hollow. Whatis meant by "hollow" is the distance measured along an axisperpendicular to the median longitudinal axis of the board, between aline connecting the widest forward portion and the widest rear portionof the board, and the edge of the board at its narrowest point.Preferably, the central hollow of the board is between 1 and 3centimeters.

In an advantageous embodiment, a straight side edge is formed betweenthe central hollow (in the form of an arc of a circle or an ellipse) andthe beginning of the tip of the board. This straight segment produces aprogressive attack during edging, and avoids overly sensitive reactionsof the board that might tend to cause the user to lose balance. The sizeof the user's support area (triangle) is reduced as a consequence of theconfiguration of the assembly of the present invention. The length ofthe straight side edge between the beginning of the tip and the curvedcentral hollow is advantageously between 2 and 25 centimeters. It isalso advantageous to provide the board with a straight side edgeextending between the central hollow and the beginning of the heel.

In a preferred embodiment, the front binding is positioned so that themiddle of the tip of the boot is situated on the median longitudinalaxis of the board, and the rear binding is positioned so that the middleof the heel of the boot is situated on the median longitudinal axis ofthe board.

In a variant, the assembly of the present invention includes a linkageplate which includes two bindings for boots, and the board includes twolongitudinal safety bindings for solidly joining the linkage plate tothe board.

In a preferred variant, the linkage plate has a diamond shape, and hasfront and rear ends suitable for cooperating with known safety bindings.Further, the linkage plate includes a rear shim (preferably with athickness between 5 and 30 millimeters) attached to the linkage plate inan angularly adjustable manner, a front shim (preferably with athickness between 5 and 30 millimeters) attached to the linkage plate inan angularly adjustable manner, and two central shims (preferably with athickness between 0 and 20 millimeters) attached to the linkage plate ina laterally adjustable manner. The bindings for the boots are solidlyjoined with the shims.

The invention will be better understood with reference to the followingdescription, together with the following drawings corresponding tonon-limiting examples of illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of an embodiment of a gliding assemblyaccording to the present invention.

FIG. 2A is an exploded isometric view of the boot bindings of theassembly of FIG. 1.

FIG. 2B is a partially sectioned, side elevational view of the assemblyof FIG. 2A.

FIG. 3 is a partially sectioned, side elevational view of an alternativeembodiment binding assembly.

FIG. 4 is a partially sectioned, top plan view of the assembly of FIG.3.

FIG. 5 is a partially sectioned, side elevational view of anotheralternative embodiment binding assembly.

FIG. 6 is a partially sectioned, top plan view of the assembly of FIG.5.

FIG. 7 is a top plan view of an alternative embodiment gliding assemblyaccording to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a first embodiment of the gliding assembly of the presentinvention. The disclosed embodiment includes a board 1 which has a tip 2at its front and a heel 3 at its rear. The total length of the boardwill vary as a function of the size and weight of the user (e.g., 178centimeters). The width of the board 1, measured at the middle of theboard, is preferably between 105 and 150 millimeters (140 millimeters inthe present example).

The central portion 4 of the board 1 has a median longitudinal axis 5.Laterally, the board 1 is defined by edges 20, 21 constituted by curvedarcs extending along the major portion of the board's length (i.e.,along the central portion). Central hollows 15 are defined between theedges 20, 21 and axes 16, 17 connecting the widest portions of the board1, at the tip 2 and the heel 3. At the middle of the board 1, thecentral hollows 15 are between 10 and 30 millimeters, and preferably onthe order of 25 millimeters. The maximum width of the board 1 is on theorder of 230 millimeters at the widest part of the tip 2 and on theorder of 220 millimeters at the widest part of the heel 3.

The edges 20, 21 are arc-shaped, and constitute a portion of a circle oran ellipse. The center of the circle forming a circular arc, or thecenter of the two foci forming an elliptical arc, is placed on an axis22, 23 perpendicular to the median longitudinal axis 5 of the board 1.In the case in which the board is symmetrical, the axis 22, 23 runsbetween the rear of the front binding and the front of the rear binding.In the case in which the board is asymmetrical, the centers of the leftand right arcs of a circle, or the midpoints of the two foci definingthe left and right elliptical arcs, are offset longitudinally, and arerespectively situated slightly behind and slightly in front of the axis22, 23 which runs through the middle of the board 1 (and the centers ofthe two bindings, with the left binding being the forwardmost binding inthe example described).

Between the beginning (the axis 25, 26) of the tip 2 and the beginningof the curved side edges 20, 21, the board 1 has a segment withsubstantially rectilinear edges 27, 28 which facilitate edge setting andimprove stability at the start of a turn. The two rectilinear segments27, 28 are of identical length, and their angle β relative to the medianlongitudinal axis 5 of the board 1 is determined by the tangent at theresulting transition point.

Straight segments 30, 31 may similarly be provided between the ends ofthe curved side edges 20, 21 and the beginning (the axis 32, 33) of theheel 3. Preferably, the length of the straight segments 30, 31 issubstantially equal to the length of the straight segments 27, 28, andis on the order of 10 centimeters, with lengths between 2 centimetersand 25 centimeters being particularly advantageous.

The central part of the board 1 allows a linkage plate 100 for thebinding of ski or snowboarding boots to be solidly joined to theboard 1. This linkage plate 100 includes two bindings 6, 7, which aredescribed in more detail with reference to FIGS. 2A and 2B. Thelongitudinal axis 8 of the front binding 6 forms an adjustable angle ofbetween 1 degree and 16 degrees with the longitudinal axis 5 of theboard 1. The longitudinal axis 9 of the rear binding 7 also forms anadjustable angle of between 1 degree and 16 degrees with thelongitudinal axis 5 of the board 1. The longitudinal axes 8, 9 of thetwo respective bindings 6, 7 are preferably parallel.

A perpendicular 10 to the longitudinal axis 5 of the board 1 which runsthrough the rear of the forwardmost binding 6 is behind, or at mostcoincides with, a perpendicular 11 to the longitudinal axis 5 of theboard 1 which runs through the front of the rearmost binding 7. Thedistance between the two perpendiculars 10, 11 is between 0 and 100millimeters, and is preferably on the order of 50 millimeters.

The board 1 includes two safety bindings 101, 102, of a known type,disposed on the median longitudinal axis 5 of the board. The bindings101, 102 are fastened (e.g., by screws) in a longitudinal direction, andare separated by a distance substantially corresponding to the length ofthe linkage plate 100 (which approximately corresponds to the length oftwo ski boots; on the order of 500 millimeters).

The linkage plate 100 is constituted by a plate which, taken as a whole,has a diamond shape. The length of the linkage plate 100, measured onthe median longitudinal axis 5, is on the order of 500 millimeters, andthe width of the linkage plate 100, measured on the median transverseaxis, is slightly less than the width of the board 1. The rear end 103of the linkage plate 100 is cut away in order to produce a rounded zonewhich extends approximately 30 degrees from both sides of the medianlongitudinal axis 5 (with a radius (curvature) on the order of 30millimeters) so as to produce the usual profile of the heel of a skiboot. The front end 104 of the linkage plate 100 is cut away in order toproduce a rounded zone which extends approximately 25 degrees from eachside of the median longitudinal axis 5 (with a radius (curvature) on theorder of 25 millimeters) so as to produce the usual profile of the toeof a ski boot.

The central part 105 of the linkage plate 100 has a rectangular shapewith a length of approximately 120 millimeters.

The rear part 106 of the linkage plate 100 has two holes 108, 109forming the coaxial arcs of a circle, which are symmetrical relative tothe median longitudinal axis 5. Likewise, the front part 110 of thelinkage plate 100 has two holes 111, 112 forming the coaxial arcs of acircle, which are symmetrical relative to the median longitudinal axis5. The central part 105 has two holes on each side of the median axis 5(113, 114 and 115, 116, respectively), which are symmetrically pairedrelative to the median longitudinal axis 5.

The holes 113, 115 are symmetrical relative to the median transverseaxis, and are constituted by the arcs of a circle having a center ofcurvature corresponding to the center 117 of the rear holes 108, 109.The angular aperture defined by the holes 113, 115 covers a sectorbetween 1 degree and 16 degrees relative to the median longitudinal axisof the linkage plate 100. The holes 114, 116 are also symmetricalrelative to the median transverse axis, and are constituted by the arcsof a circle having a center of curvature corresponding to the center 118of the front holes 111, 112. The angular aperture defined by the holes113, 115 covers a sector between 1 degree and 16 degrees relative to themedian longitudinal axis of the linkage plate 100. The cross-sections ofthe holes 108, 109, 111, 112 (FIG. 3) reveal a lower part having a widthcorresponding to the head of a fastening bolt, and an upper part havinga width corresponding to the body of the fastening bolt.

The linkage plate 100 supports a pair of bindings 120, 121 and 122, 123,respectively, for snowboarding boots of a known type. The bindings 120,121, 122, 123 are solidly joined to the linkage plate 100 by screwspassing through the holes 108, 109, 111, 112, 113, 114, 115, 116. Shims130, 131, 132, 133 are interposed between the upper surface of thelinkage plate 100 and the bindings 120, 121, 122, 123, respectively. Thefront shim 130 and the rear shim 133 interposed between the linkageplate 100 and the heel binding 120 of the rear boot 135 and the toebinding 123 of the forward boot 136, respectively, are thicker than themedian shims 131, 132. The median shims 131, 132 are positioned on twoopposing median holes 113, 116 or 114, 115. The thickness of the endmostshims 130, 133 is approximately 20 millimeters, and the thickness of themedian shims 131, 132 is approximately 10 millimeters.

The semi-circular shape of the rear holes 108, 109 and the front holes111, 112, and the elongated shape of the median holes 113, 114, 115, 116allows the angular positioning of the bindings 120, 121, 122, 123 to beadjusted between an angle of 1 degree and an angle of 16 degreesrelative to the longitudinal axis of the linkage plate 100.

The shapes of the shims 130, 131, 132, 133 are determined in order tocooperate with the profiles of the snowboarding boots 135, 136.

The linkage plate 100 has, at its rear end 106, a ski brake 140 having aconventional shape and function.

The linkage plate 100 is solidly joined with the board 1 by means of thesafety bindings 101, 102, which ensure separation of the linkage plate100 from the board 1 if the torque sustained by the user surpasses apredetermined adjustable value.

FIGS. 3 and 4 represent an alternative embodiment assembly for thebindings of a gliding apparatus according to the present invention. Thebindings include a rear safety catch 101 and a front safety catch 102 ofa known type. The catches 101, 102 are offset laterally relative to themedian longitudinal axis 5 of the board 1, and form an angle α ofapproximately 7 degrees. The two bindings 101, 102 are separated by adistance substantially equivalent to the length of two ski boots, andare fastened to the board by screws in a known manner. The rearretaining catch 101 is equipped with a ski brake 140.

The bindings further include a median retaining assembly 260 constitutedby two catches 261, 262 which are movable longitudinally relative to aguide rail 263. The front retaining catch 261 cooperates with the heelof the forwardmost boot, and is laterally offset in the exampleillustrated, toward the left of the board 1. The rear retaining catch262 cooperates with the toe of the rearwardmost boot, and is laterallyoffset in the example illustrated, toward the right of the board 1. Theguide rail 263 is disposed on the median longitudinal axis 5 of theboard 1, and ensures that the retaining elements 261, 262 are guided ina direction that is substantially parallel to the median axis 5.

A spring 264 acts on two sliding blocks 266, 267 that are solidly joinedwith the retaining catches 261, 262, respectively, and that push thecatches 261, 262 back against the ends of the boots. The spring 264 iscalibrated so as to allow the release of the boots when the stressexerted on the user's legs surpasses a predetermined value.

FIGS. 5 and 6 represent another alternative embodiment assembly for thebindings of a gliding apparatus according to the present invention. Thebindings, as in the variant of FIGS. 3 and 4, include a rear safetycatch 101 and a front safety catch 102 of a known type. The catches 101,102 are offset laterally relative to the median longitudinal axis 5,forming an angle α of approximately 7 degrees. The two bindings 101, 102are separated by a distance substantially equivalent to the length oftwo ski boots. The bindings 101, 102 are fastened to the board 1 byscrews in a known manner. The rear safety catch 101 is equipped with aski brake 140.

The binding assembly further includes two median catches 271, 272supported by a plate 273 fastened to the board 1 by screws 274, 275. Themedian catches 271, 272 are articulated relative to the fixed plate 273by two pivots 266, 267, respectively, which are substantiallyperpendicular to the surface of the board 1. The catches 271, 272 aremechanically coupled by toothed sectors 278, 279, respectively. Pivotingof one of the median catches causes the other catch to pivot along anangular course of the same amplitude. A return spring 280 assures thatthe median catches return to a neutral position in which, together withthe median longitudinal axis 5, an angle is formed which is identical tothe angle formed between the longitudinal axis of the safety catches101, 102 and the longitudinal axis 5 (e.g., of approximately 7 degrees).

FIG. 7 shows an alternative embodiment gliding apparatus according tothe present invention. In this embodiment, the total length of the board201 will again vary as a function of the size and weight of the user(e.g., 178 centimeters). The width of the board 201, measured at themiddle of the board, is preferably between 110 and 150 millimeters (140millimeters in the present example).

The central portion 204 of the board 201 has a median longitudinal axis205. The median zone of the central portion 204 of the board 201 allowstwo bindings 206, 207 for ski or snowboarding boots to be solidly joinedto the board 201. The longitudinal axis 208 of the binding 206 and thelongitudinal axis 209 of the binding 207 form an angle of approximately7 degrees with the longitudinal axis 205 of the board 201.

The perpendicular 210 to the longitudinal axis 205 of the board 201which runs through the rear of the forwardmost binding 206 is in frontof, or at most coincides with, the perpendicular 211 to the longitudinalaxis 205 of the board 201 which runs through the front of therearwardmost binding 207. The distance between the rear end of the frontbinding 206 and the front end of the rear binding 207 is between 0 and300 millimeters, and is preferably on the order of 50 millimeters. Thecenters 212, 213 of the bindings 206, 207, respectively, are offsetlaterally relative to the median longitudinal axis 205 of the board 201.

Laterally, the board 201 is defined by edges 220, 221 constituted bycurved arcs extending along the major portion of the board's length(i.e., along the central portion 4). The board includes central hollows215 (at its middle) of between 14 and 30 millimeters, and preferably onthe order of 25 millimeters. The maximum width of the board 201 is onthe order of 230 millimeters at the widest part of the tip 202 and onthe order of 220 millimeters at the widest part of the heel 203.

The edges 220, 221 constitute a portion of a circle or an ellipse. Inthe case in which the board is symmetrical, the centers of the circlesforming a circular arc or the midpoints of the two foci formingelliptical arcs, are placed on an axis which passes substantiallythrough the midpoint of the centers of the bindings 206, 207. In thecase in which the board is asymmetrical, the centers of the left andright arcs of a circle, or the midpoints of the two foci defining theleft and right elliptical arcs, are respectively situated slightlybehind and slightly in front of an axis running through the midpoint ofthe centers of the two bindings, on the axes 222, 223, respectively.

Between the beginning (the axis 225, 226) of the tip 202 and the ends ofthe curved side edges 220, 221, the board 201 has a segment withsubstantially rectilinear edges 227, 228 which facilitate edging andimprove stability at the start of a turn. The two rectilinear segments227, 228 are of identical length, and their angle β relative to themedian longitudinal axis 205 of the board 201 is determined by thetangent at the resulting transition point. Straight segments 230, 231may similarly be provided between the ends of the curved side edges 220,221 and the beginning (the axis 232, 233) of the heel 203. Preferably,the length of the straight segments 230, 231 is substantially equal tothe length of the straight segments 227, 228, and is on the order of 10centimeters, with lengths between 2 centimeters and 25 centimeters beingparticularly advantageous.

The invention is described by way of the preceding non-limitingexamples. It is to be understood that one skilled in the art will findnumerous variants without departing from the scope of the presentinvention. In particular, the dimensions are indicated for a glidingapparatus for adults. It is understood that for a gliding apparatus forchildren, the dimensions would have to be reduced proportionately.

I claim:
 1. An apparatus for gliding on snow with improved stability andbetter edge-setting in turns, comprising a single board having a mediandefining a longitudinal axis, a raised tip formed along forward portionsof the board, a heel formed along rearward portions of the board, and asafety binding assembly for securely joining boots with the board sothat the boots are prevented from moving relative to the board;whereinthe safety binding assembly includes a first binding having a mediandefining a longitudinal axis, for positioning a first boot on the board,the longitudinal axis of the first binding forming an angle with thelongitudinal axis of the board of between 0 and 20 degrees, and a secondbinding having a median defining a longitudinal axis, for positioning asecond boot on the board, the longitudinal axis of the second bindingforming an angle with the longitudinal axis of the board of between 0and 20 degrees; wherein the second binding is longitudinally andrearwardly offset relative to the first binding, along the longitudinalaxis of the board, so that the longitudinal distance from a rearwardmostpoint of the first binding to a forwardmost point of the second bindingis no greater than 100 millimeters; and wherein the board includeslaterally extending sides having center portions which are concave inshape between the tip and the heel of the board, rectilinear portionslocated where the center portions of the sides intersect with the tipand the heel of the board and further including a linkage platereceiving the first binding and the second binding and means forsecurely connecting the linkage plate to the board.
 2. The apparatus ofclaim 1 wherein the angle with the longitudinal axis of the board forthe first binding and for the second binding is between 4 and 16degrees.
 3. The apparatus of claim 1 wherein the longitudinal axis ofthe first binding is substantially parallel to the longitudinal axis ofthe second binding.
 4. The apparatus of claim 1 wherein the rearwardmostpoint of the first binding is longitudinally to the rear of theforwardmost point of the second binding, relative to the longitudinalaxis of the board.
 5. The apparatus of claim 1 wherein the rearwardmostpoint of the first binding is longitudinally in front of the forwardmostpoint of the second binding, relative to the longitudinal axis of theboard.
 6. The apparatus of claim 1 wherein the longitudinal axis of thefirst binding and the longitudinal axis of the second binding each havea midpoint, and wherein the midpoint of the longitudinal axis of thefirst binding and the midpoint of the longitudinal axis of the secondbinding is positioned on the longitudinal axis of the board.
 7. Theapparatus of claim 6 wherein the longitudinal axis of the first bindingis substantially parallel with the longitudinal axis of the secondbinding, forming an angle of approximately 7 degrees with thelongitudinal axis of the board.
 8. The apparatus of claim 7 wherein thefirst binding and the second binding have a toe portion and a heelportion, and wherein the toe portion of the first binding reaches one ofthe sides of the board and the heel portion of the second bindingreaches another of the sides of the board.
 9. The apparatus of claim 8wherein the first binding and the second binding are symmetricallypositioned on opposing sides of an axis forming an angle between 4 and16 degrees with the longitudinal axis of the board.
 10. The apparatus ofclaim 1 wherein the first binding and the second binding have a toeportion and a heel portion, and wherein the toe portion of the firstbinding and the heel portion of the second binding are positioned on thelongitudinal axis of the board, and the heel portion of the firstbinding and the toe portion of the second binding are laterally offset,on opposing sides of the longitudinal axis of the board.
 11. Theapparatus of claim 10 wherein the first binding and the second bindingare symmetrically positioned on opposing sides of an axis forming anangle between 4 and 16 degrees with the longitudinal axis of the board.12. The apparatus of claim 11 wherein the first binding and the secondbinding are symmetrically positioned on opposing sides of an axisforming an angle between 4 and 16 degrees with the longitudinal axis ofthe board.
 13. The apparatus of claim 1 wherein the board has a centerpositioned along the longitudinal axis of the board, and a width at thecenter of the board between 110 and 150 millimeters.
 14. The apparatusof claim 13 wherein the width is about 140 millimeters.
 15. Theapparatus of claim 13 wherein the board has a length of about 178centimeters.
 16. The apparatus of claim 1 wherein the concave centerportions of the sides of the board form arcs on each side of the board.17. The apparatus of claim 16 wherein the arcs define circles havingcenters which are in alignment with an axis transverse to thelongitudinal axis of the board.
 18. The apparatus of claim 16 whereinthe arcs define circles having centers which are positioned on opposingsides of an axis transverse to the longitudinal axis of the board. 19.The apparatus of claim 16 wherein the arcs define ellipses having fociwhich are aligned with each other, on opposing sides of the longitudinalaxis of the board.
 20. The apparatus of claim 19 wherein the foci of theellipses are positioned on a pair of axes transverse to the longitudinalaxis of the board.
 21. The apparatus of claim 19 wherein the foci of theellipses are offset relative to a pair of axes transverse to thelongitudinal axis of the board.
 22. The apparatus of claim 1 wherein thetip of the board has a widest portion, the heel of the board has awidest portion, and the center portions of the board have a narrowestportion, and wherein a distance extending along an axis perpendicular tothe longitudinal axis of the board and through the narrowest portion ofthe board, from each side of the board to an axis connecting each sideof the board at the widest portion of the tip and the widest portion ofthe heel, is between 1 and 3 centimeters.
 23. The apparatus of claim 1wherein the rectilinear portions include transitional portions of theedges connecting the center portions with the tip of the board.
 24. Theapparatus of claim 23 wherein the rectilinear portions further includestraight segments extending from the center portions, along the heel ofthe board.
 25. The apparatus of claim 24 wherein the straight segmentshave a length between 2 and 25 centimeters.
 26. The apparatus of claim25 wherein the length is about 10 centimeters.
 27. The apparatus ofclaim 1 wherein the connecting means includes a pair of longitudinallyspaced safety bindings positioned on the longitudinal axis of the board.28. The apparatus of claim 27 wherein the linkage plate includes frontand rear ends for cooperating with the safety bindings.
 29. Theapparatus of claim 1 wherein the linkage plate includes front and rearshims fastened to the linkage plate for angular adjustment relative tothe linkage plate, and two median shims fastened to the linkage platefor lateral adjustment relative to the linkage plate.
 30. The apparatusof claim 29 wherein the front and rear shims have a thickness between 5and 30 millimeters and the median shims have a thickness between 0 and20 millimeters, thereby placing the first binding and the second bindingat angles relative to the linkage plate and to each other.
 31. Theapparatus of claim 11 wherein the board further includes a front catch,a rear catch, and a median assembly including two retaining elementswhich are mechanically coupled and movable between a neutral positionfor engaging a toe of a rear boot and a heel of a forward boot, and asafety position for releasing the boots responsive to an excess forceexerted on the retaining elements.
 32. The apparatus of claim 31 whereinthe retaining elements of the median assembly form an angle with thelongitudinal axis of the board which corresponds to the angle formedbetween the longitudinal axes of the first binding and the secondbinding and the longitudinal axis of the board.
 33. The apparatus ofclaim 31 wherein the median assembly includes a longitudinal guide railreceiving two longitudinally movable retaining elements, wherein theretaining elements are separated by a calibrated spring.
 34. Theapparatus of claim 31 wherein the median assembly includes a fixed plateand two retaining elements which are securely joined to the fixed plate,and pivoted for rotation about two axes which are substantiallyperpendicular to surface portions of the fixed plate.
 35. The apparatusof claim 34 wherein the two retaining elements are mechanically coupledby meshing toothed sectors, and a return spring for positioning theretaining elements along opposing angles corresponding to the angleformed between the longitudinal axes of the first binding and the secondbinding and the longitudinal axis of the board.
 36. The apparatus ofclaim 31 wherein the front catch and the rear catch cooperate with themedian assembly to form an angle of approximately 7 degrees with thelongitudinal axis of the board, and wherein the median assembly ispositioned on the longitudinal axis of the board.